A Comprehensive Guide to Mobile App Development with Python

Welcome to our comprehensive guide on mobile app development with Python! In this post, we will cover everything from the basics of Python programming to advanced mobile app development frameworks. Whether you’re a beginner or an experienced developer, this guide will provide valuable insights and practical examples to help you create your own mobile applications.

Table of Contents

1. Introduction to Python
2. Setting Up Python
3. Basic Syntax and Data Types
4. Control Structures
5. Functions
6. Advanced Data Structures
7. Error Handling
8. Modules and Packages
9. Decorators
10. Generators
11. Useful Libraries and Frameworks
12. Concurrency and Parallelism
13. Advanced Python Concepts
14. Testing
15. Web Development with Flask and Django
16. Advanced Data Analysis with Pandas
17. Data Visualization with Matplotlib and Seaborn
18. Developing Mobile Applications with Python
19. Practical Project: To-Do List App
20. Additional Resources
21. Conclusion

---

1. Introduction to Python

Python is a high-level, interpreted programming language known for its readability and simplicity. It’s widely used for web development, data analysis, scientific computing, artificial intelligence, and mobile app development.

2. Setting Up Python

First, you need to have Python installed on your computer. You can download it from the official Python website. Once installed, you can use an Integrated Development Environment (IDE) like PyCharm, VSCode, or Jupyter Notebook for writing and running Python code.

3. Basic Syntax and Data Types

Learn the basics of Python syntax and fundamental data types, including integers, floats, strings, and booleans.

Hello World

print("Hello, World!")

Variables and Data Types

# Integer
a = 10

# Float
b = 3.14

# String
c = "Hello, Python"

# Boolean
d = True

Comments

# This is a single-line comment

"""
This is a
multi-line comment
"""

Practice

Exercise: Print Your Details

Write a Python script that prints your name, age, and city.

Answer:

name = "John Doe"
age = 30
city = "New York"
print(f"My name is {name}, I am {age} years old, and I live in {city}.")

Exercise: Experiment with Data Types

Experiment with different data types and print their values.

Answer:

integer_value = 42
float_value = 3.14159
string_value = "Hello, World!"
boolean_value = True

print(integer_value)
print(float_value)
print(string_value)
print(boolean_value)

4. Control Structures

Control structures are used to control the flow of execution in a program.

Conditional Statements

x = 10
if x > 5:
    print("x is greater than 5")
elif x == 5:
    print("x is equal to 5")
else:
    print("x is less than 5")

Loops

# For loop
for i in range(5):
    print(i)

# While loop
i = 0
while i < 5:
    print(i)
    i += 1

Practice

Exercise: Check Number

Write a Python program that checks if a number is positive, negative, or zero.

Answer:

number = int(input("Enter a number: "))

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")
else:
    print("The number is zero.")

Exercise: Print Numbers

Create a loop that prints numbers from 1 to 20.

Answer:

for i in range(1, 21):
    print(i)

5. Functions

Functions help you to organize your code into reusable blocks.

Defining Functions

def greet(name):
    return f"Hello, {name}"

print(greet("Alice"))

Practice

Exercise: Factorial Function

Write a function that calculates the factorial of a number.

Answer:

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)

print(factorial(5))  # Output: 120

Exercise: Palindrome Checker

Create a function that checks if a string is a palindrome.

Answer:

def is_palindrome(s):
    return s == s[::-1]

print(is_palindrome("radar"))  # Output: True
print(is_palindrome("hello"))  # Output: False

6. Advanced Data Structures

Learn about list comprehensions, dictionary comprehensions, and more.

List Comprehensions

# Create a list of squares
squares = [x ** 2 for x in range(10)]
print(squares)

Dictionary Comprehensions

# Create a dictionary with numbers and their squares
squares_dict = {x: x ** 2 for x in range(10)}
print(squares_dict)

Practice

Exercise: Even Numbers

Use list comprehensions to create a list of even numbers from 1 to 20.

Answer:

even_numbers = [x for x in range(1, 21) if x % 2 == 0]
print(even_numbers)

Exercise: Cubes Dictionary

Create a dictionary that maps numbers to their cubes.

Answer:

cubes_dict = {x: x ** 3 for x in range(1, 11)}
print(cubes_dict)

7. Error Handling

Error handling in Python is done using try and except blocks.

Try-Except Blocks

try:
    result = 10 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")

Custom Exceptions

class CustomError(Exception):
    pass

try:
    raise CustomError("This is a custom error")
except CustomError as e:
    print(e)

Practice

Exercise: File Reading Error

Write a program that handles file reading errors.

Answer:

try:
    with open("non_existent_file.txt", "r") as file:
        content = file.read()
except FileNotFoundError:
    print("File not found!")

Exercise: Custom Exception

Create a custom exception for invalid inputs in a function.

Answer:

class InvalidInputError(Exception):
    pass

def check_positive(number):
    if number < 0:
        raise InvalidInputError("Negative numbers are not allowed.")
    return number

try:
    print(check_positive(-5))
except InvalidInputError as e:
    print(e)

8. Modules and Packages

Learn how to create and use modules and packages in Python.

Creating Modules

# my_module.py
def greet(name):
    return f"Hello, {name}"

# main.py
import my_module

print(my_module.greet("Alice"))

Creating Packages

# my_package/__init__.py
# my_package/module1.py
# my_package/module2.py

Practice

Exercise: Shape Area Module

Create a module with a function that calculates the area of different shapes.

Answer:

# shapes.py
def area_of_circle(radius):
    return 3.14159 * radius ** 2

def area_of_rectangle(length, width):
    return length * width

# main.py
import shapes

print(shapes.area_of_circle(5))      # Output: 78.53975
print(shapes.area_of_rectangle(4, 6)) # Output: 24

Exercise: Organize Code into Packages

Organize your code into packages and import them in a main script.

Answer:

# my_package/__init__.py
# my_package/module1.py
def greet(name):
    return f"Hello, {name}"

# my_package/module2.py
def farewell(name):
    return f"Goodbye, {name}"

# main.py
from my_package import module1, module

2

print(module1.greet("Alice"))
print(module2.farewell("Bob"))

9. Decorators

Decorators are a powerful tool to modify the behavior of functions or classes.

Function Decorators

def my_decorator(func):
    def wrapper():
        print("Something is happening before the function is called.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

say_hello()

Class Decorators

def add_methods(cls):
    cls.new_method = lambda self: print("New method added")
    return cls

@add_methods
class MyClass:
    pass

obj = MyClass()
obj.new_method()

Practice

Exercise: Execution Time Logger

Create a decorator that logs the execution time of a function.

Answer:

import time

def time_logger(func):
    def wrapper(*args, **kwargs):
        start_time = time.time()
        result = func(*args, **kwargs)
        end_time = time.time()
        print(f"Execution time: {end_time - start_time} seconds")
        return result
    return wrapper

@time_logger
def slow_function():
    time.sleep(2)
    print("Function finished")

slow_function()

Exercise: Class Method Adder

Implement a class decorator that adds a new method to a class.

Answer:

def add_greeting(cls):
    cls.greet = lambda self: print("Hello, world!")
    return cls

@add_greeting
class MyClass:
    pass

obj = MyClass()
obj.greet()

10. Generators

Generators allow you to iterate over data without storing the entire dataset in memory.

def my_generator():
    for i in range(10):
        yield i

for value in my_generator():
    print(value)

Practice

Exercise: Even Number Generator

Write a generator function that yields even numbers up to a given limit.

Answer:

def even_numbers(limit):
    for i in range(limit + 1):
        if i % 2 == 0:
            yield i

for num in even_numbers(10):
    print(num)

Exercise: Line by Line File Reader

Use a generator to read large files line by line.

Answer:

def read_lines(file_path):
    with open(file_path, "r") as file:
        for line in file:
            yield line.strip()

for line in read_lines("large_file.txt"):
    print(line)

11. Useful Libraries and Frameworks

Explore libraries like NumPy, Pandas, Matplotlib, Flask, and Django.

NumPy

import numpy as np

array = np.array([1, 2, 3, 4, 5])
print(array.mean())

Pandas

import pandas as pd

data = {'Name': ['Alice', 'Bob', 'Charlie'], 'Age': [25, 30, 35]}
df = pd.DataFrame(data)
print(df)

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 20, 25, 30, 35]

plt.plot(x, y)
plt.xlabel('x-axis')
plt.ylabel('y-axis')
plt.title('Sample Plot')
plt.show()

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return "Hello, Flask!"

if __name__ == '__main__':
    app.run(debug=True)

Django

# This is an example of a simple Django view

from django.http import HttpResponse

def home(request):
    return HttpResponse("Hello, Django!")

Practice

Exercise: NumPy Operations

Create a NumPy array and perform basic arithmetic operations.

Answer:

import numpy as np

array = np.array([1, 2, 3, 4, 5])
print(array + 10)
print(array * 2)
print(array.mean())

Exercise: Load CSV with Pandas

Load a CSV file using Pandas and perform data analysis.

Answer:

import pandas as pd

df = pd.read_csv("data.csv")
print(df.head())
print(df.describe())

Exercise: Plot Graph with Matplotlib

Plot a simple graph using Matplotlib.

Answer:

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 20, 25, 30, 35]

plt.plot(x, y, marker='o')
plt.xlabel('X-axis')
plt.ylabel('Y-axis')
plt.title('Sample Plot')
plt.show()

Exercise: Flask Web App

Build a basic web application using Flask.

Answer:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return "Welcome to my Flask app!"

@app.route('/about')
def about():
    return "This is the about page."

if __name__ == '__main__':
    app.run(debug=True)

Exercise: Django Project

Create a simple Django project and add new views.

Answer:

# Install Django
pip install django

# Create a new Django project
django-admin startproject myproject

# Create a new app
cd myproject
python manage.py startapp myapp

# Add 'myapp' to INSTALLED_APPS in settings.py
# Create a view in myapp/views.py
from django.http import HttpResponse

def home(request):
    return HttpResponse("Hello, Django!")

def about(request):
    return HttpResponse("About this site")

# Add the view to myapp/urls.py
from django.urls import path
from . import views

urlpatterns = [
    path('', views.home),
    path('about/', views.about),
]

# Include myapp.urls in myproject/urls.py
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('myapp.urls')),
]

# Run the server
python manage.py runserver

12. Concurrency and Parallelism

Learn about threading and multiprocessing for concurrent and parallel execution.

Threading

import threading

def print_numbers():
    for i in range(10):
        print(i)

thread = threading.Thread(target=print_numbers)
thread.start()

Multiprocessing

import multiprocessing

def print_numbers():
    for i in range(10):
        print(i)

process = multiprocessing.Process(target=print_numbers)
process.start()

Practice

Exercise: Multithreading

Create a multithreaded program that prints numbers in parallel.

Answer:

import threading

def print_numbers():
    for i in range(5):
        print(f"Thread {threading.current_thread().name}: {i}")

threads = []
for i in range(3):
    thread = threading.Thread(target=print_numbers, name=f"Thread-{i}")
    threads.append(thread)
    thread.start()

for thread in threads:
    thread.join()

Exercise: Multiprocessing Tasks

Implement a multiprocessing program to perform computational tasks.

Answer:

import multiprocessing

def compute_square(n):
    print(f"The square of {n} is {n * n}")

numbers = [1, 2, 3, 4, 5]
processes = []

for number in numbers:
    process = multiprocessing.Process(target=compute_square, args=(number,))
    processes.append(process)
    process.start()

for process in processes:
    process.join()

13. Advanced Python Concepts

Explore context managers, type hinting, and more.

Context Managers

with open("example.txt", "w") as file:
    file.write("Hello, World!")

Type Hinting

def greeting(name: str) -> str:
    return f"Hello, {name}"

print(greeting("Alice"))

Practice

Exercise: Custom Context Manager

Create a custom context manager using __enter__ and __exit__ methods.

Answer:

class CustomContextManager:
    def __enter__(self):
        print("Entering context")
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        print("Exiting context")

with CustomContextManager():
    print("Inside context")

Exercise: Add Type Hints

Add type hints to your functions and classes.

Answer:

def add(a: int, b: int) -> int:
    return a + b

class Person:
    def __init__(self, name: str, age: int):
        self.name = name
        self.age = age

    def greet(self) -> str:
        return f"Hello, my name is {self.name} and I am {self.age} years old."

person = Person("Alice", 30)
print(person.greet())

14. Testing

Learn how to write unit tests using unittest and pytest.

Unit Testing with unittest

import unittest

def add(a, b):


 return a + b

class TestMath(unittest.TestCase):
    def test_add(self):
        self.assertEqual(add(1, 2), 3)

if __name__ == '__main__':
    unittest.main()

Unit Testing with pytest

# Save this in a file named test_example.py
def add(a, b):
    return a + b

def test_add():
    assert add(1, 2) == 3
    assert add(-1, 1) == 0
    assert add(0, 0) == 0

# Run the tests with: pytest test_example.py

Practice

Exercise: Unit Tests with unittest

Write unit tests for your functions using unittest.

Answer:

import unittest

def multiply(a, b):
    return a * b

class TestMath(unittest.TestCase):
    def test_multiply(self):
        self.assertEqual(multiply(2, 3), 6)
        self.assertEqual(multiply(-1, 1), -1)
        self.assertEqual(multiply(0, 5), 0)

if __name__ == '__main__':
    unittest.main()

Exercise: Parameterized Tests with pytest

Use pytest to create parameterized tests.

Answer:

import pytest

@pytest.mark.parametrize("a,b,expected", [
    (1, 2, 3),
    (2, 3, 5),
    (3, 4, 7),
])
def test_add(a, b, expected):
    assert add(a, b) == expected

# Run the tests with: pytest test_example.py

15. Web Development with Flask and Django

Build web applications using Flask and Django.

Flask – REST API

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/api', methods=['GET'])
def get_data():
    return jsonify({"message": "Hello, World!"})

@app.route('/api', methods=['POST'])
def post_data():
    data = request.json
    return jsonify(data), 201

if __name__ == '__main__':
    app.run(debug=True)

Django – Basic Setup

# Install Django
pip install django

# Create a new Django project
django-admin startproject myproject

# Create a new app
cd myproject
python manage.py startapp myapp

# Add 'myapp' to INSTALLED_APPS in settings.py
# Create a view in myapp/views.py
from django.http import HttpResponse

def home(request):
    return HttpResponse("Hello, Django!")

def about(request):
    return HttpResponse("About this site")

# Add the view to myapp/urls.py
from django.urls import path
from . import views

urlpatterns = [
    path('', views.home),
    path('about/', views.about),
]

# Include myapp.urls in myproject/urls.py
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('myapp.urls')),
]

# Run the server
python manage.py runserver

Practice

Exercise: Flask REST API

Create a simple REST API using Flask.

Answer:

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/api/greet', methods=['GET'])
def greet():
    name = request.args.get('name', 'World')
    return jsonify({"message": f"Hello, {name}!"})

if __name__ == '__main__':
    app.run(debug=True)

Exercise: Django Views

Build a basic website with Django and add new views.

Answer:

# Install Django
pip install django

# Create a new Django project
django-admin startproject myproject

# Create a new app
cd myproject
python manage.py startapp myapp

# Add 'myapp' to INSTALLED_APPS in settings.py
# Create a view in myapp/views.py
from django.http import HttpResponse

def home(request):
    return HttpResponse("Hello, Django!")

def contact(request):
    return HttpResponse("Contact us at contact@example.com")

# Add the view to myapp/urls.py
from django.urls import path
from . import views

urlpatterns = [
    path('', views.home),
    path('contact/', views.contact),
]

# Include myapp.urls in myproject/urls.py
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('myapp.urls')),
]

# Run the server
python manage.py runserver

16. Advanced Data Analysis with Pandas

Perform advanced data analysis with Pandas.

Grouping and Aggregation

import pandas as pd

data = {'Name': ['Alice', 'Bob', 'Charlie', 'Alice', 'Bob'],
        'Score': [85, 92, 78, 95, 85]}
df = pd.DataFrame(data)

# Group by name and calculate mean score
grouped = df.groupby('Name').mean()
print(grouped)

Merging DataFrames

data1 = {'Name': ['Alice', 'Bob', 'Charlie'],
         'Age': [25, 30, 35]}
df1 = pd.DataFrame(data1)

data2 = {'Name': ['Alice', 'Bob', 'David'],
         'Salary': [70000, 80000, 90000]}
df2 = pd.DataFrame(data2)

merged = pd.merge(df1, df2, on='Name', how='outer')
print(merged)

Practice

Exercise: Group and Aggregate

Load a dataset and perform grouping and aggregation.

Answer:

import pandas as pd

data = {'Department': ['Sales', 'HR', 'IT', 'Sales', 'IT'],
        'Employee': ['Alice', 'Bob', 'Charlie', 'David', 'Eve'],
        'Salary': [50000, 60000, 70000, 55000, 65000]}
df = pd.DataFrame(data)

# Group by department and calculate mean salary
grouped = df.groupby('Department')['Salary'].mean()
print(grouped)

Exercise: Merge DataFrames

Merge two DataFrames and perform data analysis.

Answer:

data1 = {'Employee': ['Alice', 'Bob', 'Charlie'],
         'Department': ['Sales', 'HR', 'IT']}
df1 = pd.DataFrame(data1)

data2 = {'Employee': ['Alice', 'Charlie', 'Eve'],
         'Project': ['Project A', 'Project B', 'Project C']}
df2 = pd.DataFrame(data2)

merged = pd.merge(df1, df2, on='Employee', how='outer')
print(merged)

17. Data Visualization with Matplotlib and Seaborn

Visualize data using Matplotlib and Seaborn.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 20, 25, 30, 35]

plt.plot(x, y, marker='o')
plt.xlabel('X-axis')
plt.ylabel('Y-axis')
plt.title('Sample Plot')
plt.show()

Seaborn

import seaborn as sns
import pandas as pd

data = {'X': [1, 2, 3, 4, 5], 'Y': [10, 20, 25, 30, 35]}
df = pd.DataFrame(data)

sns.lineplot(x='X', y='Y', data=df)
plt.title('Sample Seaborn Plot')
plt.show()

Practice

Exercise: Matplotlib Line Plot

Create a line plot using Matplotlib.

Answer:

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 20, 30, 40, 50]

plt.plot(x, y, marker='o')
plt.xlabel('X-axis')
plt.ylabel('Y-axis')
plt.title('Line Plot Example')
plt.grid(True)
plt.show()

Exercise: Seaborn Visualization

Use Seaborn to visualize a dataset.

Answer:

import seaborn as sns
import pandas as pd

data = {'Category': ['A', 'B', 'C', 'A', 'B', 'C'],
        'Values': [10, 20, 15, 25, 30, 35]}
df = pd.DataFrame(data)

sns.barplot(x='Category', y='Values', data=df)
plt.title('Seaborn Bar Plot Example')
plt.show()

18. Developing Mobile Applications with Python

Explore various frameworks for developing mobile applications using Python, such as Kivy, BeeWare, and Python-for-Android.

Kivy

Kivy is an open-source Python library for developing multitouch applications. It runs on Linux, Windows, OS X, Android, and iOS.

Basic Kivy Application

from kivy.app import App
from kivy.uix.label import Label

class MyApp(App):
    def build(self):
        return Label(text="Hello, Kivy!")

if __name__ ==

 '__main__':
    MyApp().run()

BeeWare

BeeWare allows you to write native applications in Python for iOS, Android, and other platforms.

Basic BeeWare Application

import toga
from toga.style import Pack
from toga.style.pack import COLUMN, ROW

class MyApp(toga.App):
    def startup(self):
        main_box = toga.Box(style=Pack(direction=COLUMN))

        name_label = toga.Label('Your name: ', style=Pack(padding=(0, 5)))
        self.name_input = toga.TextInput(style=Pack(flex=1))

        greet_button = toga.Button(
            'Greet',
            on_press=self.say_hello,
            style=Pack(padding=5)
        )

        main_box.add(name_label)
        main_box.add(self.name_input)
        main_box.add(greet_button)

        self.main_window = toga.MainWindow(title=self.formal_name)
        self.main_window.content = main_box
        self.main_window.show()

    def say_hello(self, widget):
        print(f"Hello, {self.name_input.value}!")

def main():
    return MyApp()

if __name__ == '__main__':
    main().main_loop()

Python-for-Android (p4a)

Python-for-Android is a tool to create standalone Android APKs.

Creating an APK

p4a create --dist_name=myapp --bootstrap=sdl2 --requirements=kivy --package=org.example.myapp --name "MyApp" --version=0.1
cd myapp
p4a apk --dist_name=myapp --release --signkey=~/path/to/your.keystore

KivyMD

KivyMD is a collection of Material Design widgets for use with Kivy.

Basic KivyMD Application

from kivymd.app import MDApp
from kivymd.uix.label import MDLabel

class MyApp(MDApp):
    def build(self):
        return MDLabel(text="Hello, KivyMD!", halign="center")

if __name__ == '__main__':
    MyApp().run()

Practice

Exercise: Kivy Mobile App

Create a basic mobile application using Kivy.

Answer:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.label import Label

class MyApp(App):
    def build(self):
        layout = BoxLayout(orientation='vertical')
        self.label = Label(text="Press the button")
        button = Button(text="Press me", on_press=self.on_button_press)
        layout.add_widget(self.label)
        layout.add_widget(button)
        return layout

    def on_button_press(self, instance):
        self.label.text = "Button pressed!"

if __name__ == '__main__':
    MyApp().run()

Exercise: BeeWare App

Develop a simple app with BeeWare and deploy it on your mobile device.

Answer:

import toga
from toga.style import Pack
from toga.style.pack import COLUMN, ROW

class MyApp(toga.App):
    def startup(self):
        main_box = toga.Box(style=Pack(direction=COLUMN))

        self.label = toga.Label('Press the button', style=Pack(padding=(0, 5)))
        button = toga.Button('Press me', on_press=self.on_button_press, style=Pack(padding=5))

        main_box.add(self.label)
        main_box.add(button)

        self.main_window = toga.MainWindow(title=self.formal_name)
        self.main_window.content = main_box
        self.main_window.show()

    def on_button_press(self, widget):
        self.label.text = "Button pressed!"

def main():
    return MyApp()

if __name__ == '__main__':
    main().main_loop()

Exercise: Python-for-Android APK

Use Python-for-Android to package a Kivy application into an APK.

Answer:

# Ensure you have the necessary dependencies installed
pip install python-for-android

# Create the Kivy app directory and main.py file
mkdir mykivyapp
cd mykivyapp
echo "from kivy.app import App\nfrom kivy.uix.label import Label\n\nclass MyApp(App):\n    def build(self):\n        return Label(text='Hello, Kivy!')\n\nif __name__ == '__main__':\n    MyApp().run()" > main.py

# Build the APK
p4a create --dist_name=mykivyapp --bootstrap=sdl2 --requirements=kivy --package=org.example.mykivyapp --name "MyKivyApp" --version=0.1
cd mykivyapp
p4a apk --dist_name=mykivyapp --release --signkey=~/path/to/your.keystore

19. Practical Project: To-Do List App

Let’s put everything together and create a complete project: a To-Do List App using Kivy and SQLite.

Installing Dependencies

pip install kivy sqlite3

Main Application Code

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
import sqlite3

class ToDoApp(App):
    def build(self):
        self.conn = sqlite3.connect('todos.db')
        self.create_table()

        self.layout = BoxLayout(orientation='vertical')
        self.task_input = TextInput(hint_text='Enter a task')
        self.layout.add_widget(self.task_input)

        self.add_button = Button(text='Add Task', on_press=self.add_task)
        self.layout.add_widget(self.add_button)

        self.tasks_layout = BoxLayout(orientation='vertical')
        self.layout.add_widget(self.tasks_layout)

        self.display_tasks()
        return self.layout

    def create_table(self):
        with self.conn:
            self.conn.execute('CREATE TABLE IF NOT EXISTS tasks (id INTEGER PRIMARY KEY, task TEXT)')

    def add_task(self, instance):
        task = self.task_input.text
        if task:
            with self.conn:
                self.conn.execute('INSERT INTO tasks (task) VALUES (?)', (task,))
            self.task_input.text = ''
            self.display_tasks()

    def display_tasks(self):
        self.tasks_layout.clear_widgets()
        cursor = self.conn.execute('SELECT * FROM tasks')
        for row in cursor:
            task_label = Label(text=row[1])
            self.tasks_layout.add_widget(task_label)

    def on_stop(self):
        self.conn.close()

if __name__ == '__main__':
    ToDoApp().run()

Practice

Exercise: Extend To-Do List App

Extend the To-Do List App to include functionality for deleting and updating tasks.

Answer:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.gridlayout import GridLayout
import sqlite3

class ToDoApp(App):
    def build(self):
        self.conn = sqlite3.connect('todos.db')
        self.create_table()

        self.layout = BoxLayout(orientation='vertical')
        self.task_input = TextInput(hint_text='Enter a task')
        self.layout.add_widget(self.task_input)

        self.add_button = Button(text='Add Task', on_press=self.add_task)
        self.layout.add_widget(self.add_button)

        self.tasks_layout = GridLayout(cols=3)
        self.layout.add_widget(self.tasks_layout)

        self.display_tasks()
        return self.layout

    def create_table(self):
        with self.conn:
            self.conn.execute('CREATE TABLE IF NOT EXISTS tasks (id INTEGER PRIMARY KEY, task TEXT)')

    def add_task(self, instance):
        task = self.task_input.text
        if task:
            with self.conn:
                self.conn.execute('INSERT INTO tasks (task) VALUES (?)', (task,))
            self.task_input.text = ''
            self.display_tasks()

    def delete_task(self, task_id):
        with self.conn:
            self.conn.execute('DELETE FROM tasks WHERE id = ?', (task_id,))
        self.display_tasks()

    def update_task(self, task_id, new_task):
        with self.conn:
            self.conn.execute('UPDATE tasks SET task = ? WHERE id = ?', (new_task, task_id))
        self.display_tasks()

    def display_tasks(self):
        self.tasks_layout.clear_widgets()
        cursor = self.conn.execute('SELECT * FROM tasks')
        for row in cursor:
            task_id, task_text = row
            task_label = Label(text=task_text)
            delete_button = Button(text='Delete', on_press=lambda instance, task_id=task_id: self.delete_task(task_id))
            update_button = Button(text='Update', on_press=lambda instance, task_id=task_id: self.update_task(task_id, self.task_input.text))
            self.tasks_layout.add_widget(task_label)
            self.tasks_layout.add_widget(delete_button)
            self.tasks_layout.add_widget(update_button)

    def on_stop(self):
        self.conn.close()

if __name__ == '__main__':
    ToDoApp().run()

Exercise: Mark Tasks as Completed

Add a feature to mark tasks as completed.

Answer:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.textinput import TextInput
from kivy.uix.button import

 Button
from kivy.uix.gridlayout import GridLayout
from kivy.properties import BooleanProperty
import sqlite3

class ToDoApp(App):
    def build(self):
        self.conn = sqlite3.connect('todos.db')
        self.create_table()

        self.layout = BoxLayout(orientation='vertical')
        self.task_input = TextInput(hint_text='Enter a task')
        self.layout.add_widget(self.task_input)

        self.add_button = Button(text='Add Task', on_press=self.add_task)
        self.layout.add_widget(self.add_button)

        self.tasks_layout = GridLayout(cols=4)
        self.layout.add_widget(self.tasks_layout)

        self.display_tasks()
        return self.layout

    def create_table(self):
        with self.conn:
            self.conn.execute('CREATE TABLE IF NOT EXISTS tasks (id INTEGER PRIMARY KEY, task TEXT, completed BOOLEAN)')

    def add_task(self, instance):
        task = self.task_input.text
        if task:
            with self.conn:
                self.conn.execute('INSERT INTO tasks (task, completed) VALUES (?, ?)', (task, False))
            self.task_input.text = ''
            self.display_tasks()

    def delete_task(self, task_id):
        with self.conn:
            self.conn.execute('DELETE FROM tasks WHERE id = ?', (task_id,))
        self.display_tasks()

    def update_task(self, task_id, new_task):
        with self.conn:
            self.conn.execute('UPDATE tasks SET task = ? WHERE id = ?', (new_task, task_id))
        self.display_tasks()

    def toggle_task_completion(self, task_id, current_state):
        with self.conn:
            self.conn.execute('UPDATE tasks SET completed = ? WHERE id = ?', (not current_state, task_id))
        self.display_tasks()

    def display_tasks(self):
        self.tasks_layout.clear_widgets()
        cursor = self.conn.execute('SELECT * FROM tasks')
        for row in cursor:
            task_id, task_text, completed = row
            task_label = Label(text=task_text, color=(0, 1, 0, 1) if completed else (1, 0, 0, 1))
            delete_button = Button(text='Delete', on_press=lambda instance, task_id=task_id: self.delete_task(task_id))
            update_button = Button(text='Update', on_press=lambda instance, task_id=task_id: self.update_task(task_id, self.task_input.text))
            toggle_button = Button(text='Complete' if not completed else 'Uncomplete', on_press=lambda instance, task_id=task_id, current_state=completed: self.toggle_task_completion(task_id, current_state))
            self.tasks_layout.add_widget(task_label)
            self.tasks_layout.add_widget(delete_button)
            self.tasks_layout.add_widget(update_button)
            self.tasks_layout.add_widget(toggle_button)

    def on_stop(self):
        self.conn.close()

if __name__ == '__main__':
    ToDoApp().run()

20. Additional Resources

Here are some additional free resources to help you learn and practice Python and mobile app development:

Online Courses

• Coursera: Python for Everybody – Free to audit.
• edX: Introduction to Computer Science using Python – Free to audit.
• Khan Academy: Intro to Python – Free to access.

Books and Tutorials

• Automate the Boring Stuff with Python by Al Sweigart – Free to read online.
• W3Schools Python Tutorial – Free online tutorial.
• Real Python – Free tutorials and articles.

Tools

• PyCharm Community Edition – Free IDE for Python.
• Visual Studio Code – Free code editor with Python support.
• Jupyter Notebook – Free tool for interactive data science and scientific computing.

Practice Platforms

• LeetCode – Free coding challenges and practice problems.
• HackerRank – Free coding challenges and practice problems.
• Codewars – Free coding challenges and practice problems.

21. Conclusion

We hope this guide has provided you with valuable insights into mobile app development using Python. At New Waves App Development, we specialize in creating high-quality mobile applications tailored to your needs. Contact us via WhatsApp https://wa.me/97455574988, call +97455574988, or email info@new-waves.net to discuss your app development needs.

---

By following these steps and using the provided code snippets, you can start developing mobile applications with Python. Happy coding!